Lifting-jack.



No. 768,182. P'ATENTBD AUGl l23, 1904,

. W. JOHNSTON LIETING JACK.

APPLIGATON r LED 001226, 1903.

No MODEL.

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No.- 768,182.Y

I UNITEI) STATES Patented August 23, 1904.

PATENT OFFICE.

' WILLIAM A. JOHNSTON, OF RURAL RETREAT, VIRGINIA, ASSIGNOR OF ONE-HALF TO WILLIAM WASHINGTON BUCK, OF RURAL RETREAT,

VIRGINIA.

LlFTlNG-JACK.

SPECIFICATION forming part of Letters Patent No. r768,182, dated August 23, 1904.

Application filed october 26,1903?.

Be it known tllat I, WILLIAM A. JOHNSTON, a citizen of the United States, residing at Rural Retreat, in the county of VVythe and State of Virginia, have invented a new and `useful Lifting-Jack, of which the following is a specification. v

This invention relates to certain improvements in lifting-jacks, and has for its principal object to provide an improved form of mechanical jack in which heavy loads may be raised with comparatively slight exertion on the part of the operator.

A further object of the invention is to construct a jack in which the lifting force is applied to the load-carrying platform at a plu'' rality of points, the jack being in a measure self-balancing, so that a heavy load applied at one point will tend to elevate the platform at the other point of connection with the elevating means.

A still further object of the invention is to providea jack in which a load-carrying platform is connected mechanically to an elevating means, the platform being' so arranged that a heavy load at one side of the platform will exert force tllrough suitable leverage, preferably in the form of gears, in such manner that it may exercise a lifting force on the opplosite side of the platform and onthe load itse f.

A still further object of the invention is to construct a "mechanically-actuated jack in which the load-receiving platform automatically balances itself to they load and in which manual vforce may be transmitted through suitable gearing connections to exert' lifting force atall points of connection between the elevating mechanism and the platform.

With these and other objects in view, aswill hereinafter appear more fully, the invention consists in the novel construction and arrangement of parts hereinafter described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various 'in the top thereof.

changes in the form, proportions, size, and

serial No. 178,591. (No model.)

minor details of the structure may be made without departing from thespirit or sacrificing any of the advantages of the invention.

In the accompanying drawings, Figure l isa longitudinal sectional elevation of a liftingjack constructed in accordance with the invention. Fig. 2 is a sectional plan view of the yance with the character of the work to be performed. l The lifting-table Q iscarried by two rackbars 3 and 4t, that are arranged in suitable guides near the opposite sides of the casing and extend upward through suitable openings The connection between the platform and the rack-bars is pivotal in order that the platform may tilt to accommodate itself tothe load, the connection between the rack 4 of the platform being so arranged vas to permit of considerable lateral play of the leverage force on the platform the gear and pinion are shifted lengthwise of the shaft un-A til the pinion 7 is opposite the rack 4t.y The lower portion of the rack 4t is provided with a vertical slot 9,. into which extends a screw 10,' adapted to a threaded opening in the frame or casing, and by turning this screw the rack may be forced in the direction of the shaft until its teeth interm esh with those of the pinion 7, and this movement ispermitted by the connection between the upper end of the vrackbar and the platform.

The casing is provided with a pair of inwardly-extending ribs 11, provided with guiding-grooves 12, into which extend the opposite sides of a double'racl-bar 13, one set of teeth of said raclebar intermeshing with the teeth of the gear 8 at all times and without regard to the position to which the gear may be adjusted, the width of the gear being sufiieient to maintain the parts in operative relation when the g'ear and pinion are adjusted to bring the latter in mesh with the rack-bar 4.

At one side of the casing is a vertically-disposed slot 14, through which extends a floating shaft 15, carrying a pinion 16, the teeth of which intermesh with those of a rack-bar 3 and with one of the sets of teeth on the double raelebar 13. 'Ihat end of the shaft 15 which extends through the slot is provided with a handled operating-crank 17, which may be turned manually in order to apply lifting force to the platform. rlhe lifting power is exerted by turning the crank 17, and this acts through the oating gear to elevate the rack 3 and depress the rack 13. As the rack 13 moves downward it turns the gear 8, and upward movement of the latter on the opposite side elevates the rack-bar 4, and as the surface speed of all of the gears and pinions is equal the lifting power applied to the two racks will be uniform. If it is desired to increase the leverage force, the gear 7 and pinion 8 are shifted lengthwise of shaft 6 until the pinion 7 is opposite the rack-bar 4. The latter is then forced inward by means of screw 10 until its teeth intermesh with those of the pinion, while the gear still remains in mesh with the rack-bar 13. When the iioating gear is turned, the downward stress on rack-bar 13 will exercise a lifting force on the rack-bar 4 proportionate to the length of the levers represented by the radii of the pinion 7 and gear 8, while the ioating gear will gradually descend. so that the racks 3 and 4 will be elevated at the same speed.

vA liftingjack constructed in accordance with this invention may be employed for the purpose of lifting loads of any character, and the size of the platform, the gears, and frame may be altered in accordance with the character of the work to be performed without departing from the invention.

Having thus described the invention, what is claimed isA l. In a lifting-jack, a load-receiving platform, a pair of rack-bars connected thereto,

and means including a floating gear, for connecting the rack-bars to each other.

Q. In a lifting-jack, a load-receiving platform, a pair of rack-bars connected thereto, an intermediate double rack, and gears connecting the several racks in series.

3. In a lifting-jack. a load-receiving platform, a pair of rack-hars connected thereto, a double rack-bar, a iioating gear connecting one of the platform-bars to the double rackbar, and a second gear connecting the double rael-bar to the second platform-bar.

4. In a lifting-jack, a load-receiving platform, a pair of rack-bars connected thereto, a double rack-bar, a floating gear connecting the double rack-bar to one of the platformbars, an operating-crank connected to the lioating gear, and a second gear connecting the double rack-bar tothe second platform-Imi'.

5. In a lifting-jack, a load-receiving platform, a pair of rack-bars pivotally connected thereto, an intermediate double rack-har, a floating gear connecting one of the pivoted racks to the double rack, a shaft, a gear and pinion adjustable longitudinally of the shaft, the gear-wheel being' in mesh with the double rack, and means for adjusting the second rackbar to intermesh with either the gear or the pinion.

6. In a lifting-jack, a frame having a vertically-disposed slot, an operatingeshaft extending therethrough and provided with a crank, a gear mounted on the shaft, a pair of spaced ribs extending inward from opposite sides of the frame and provided with guidinggrooves, a double rack-bar adapted to said Agrooves andy intermeshing with said gear, a

raclebar intermeshing with the gear, a loadreceiving platform to which said rack-bar is pivotally connected, a second rack-har also pivotally connected to the platform, a shaft, a gear and pinion mounted on the shaft and adjustable longitudinally thereof, said gear being in mesh with the double rack-har, and a screw for adjusting the second rack-bar in position to engage either the longitudinallyadjustable gear or the pinion.

In testimony that I claim the foregoing as my own I have hereto ai'lixed my signature in the presence of two witnesses.

WILLIAM A. JOHNSTON.

I/Vitnesses:

J. H. JoouUM, Jr., J. Ross CoLuoUN.

lOO 

